U.S. patent application number 11/600287 was filed with the patent office on 2008-04-03 for method and system for designing smooth surfaces for vehicle parts.
This patent application is currently assigned to AIRBUS ESPANA, S.L.. Invention is credited to Juan Ramon Perez Garraleta.
Application Number | 20080082192 11/600287 |
Document ID | / |
Family ID | 39230566 |
Filed Date | 2008-04-03 |
United States Patent
Application |
20080082192 |
Kind Code |
A1 |
Perez Garraleta; Juan
Ramon |
April 3, 2008 |
Method and system for designing smooth surfaces for vehicle
parts
Abstract
The invention relates to a method and system for designing a
smooth surface (13) for a vehicle part, such as the hull of an
aircraft, covering an area of its body (11) organized around an
axis X, comprising the following steps: Providing data indicating
the profile, area and the position of a plurality of sectors (15)
perpendicular to axis X of said smooth surface (13); Generating a
first surface from said data by using a NURBS mathematical
methodology; Modifying N1 equidistant profiles (Py) of said surface
until their area (APy) is consistent with the area determined by
the area curve resulting from the data of the first step;
Generating a second surface from said profiles (Py) and validating
that it adjusts to the area curve by using N2 equidistant profiles
of said surface, where N2>N1.
Inventors: |
Perez Garraleta; Juan Ramon;
(Madrid, ES) |
Correspondence
Address: |
LADAS & PARRY
26 WEST 61ST STREET
NEW YORK
NY
10023
US
|
Assignee: |
AIRBUS ESPANA, S.L.
|
Family ID: |
39230566 |
Appl. No.: |
11/600287 |
Filed: |
November 15, 2006 |
Current U.S.
Class: |
700/98 |
Current CPC
Class: |
G06F 30/15 20200101 |
Class at
Publication: |
700/98 |
International
Class: |
G06F 19/00 20060101
G06F019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2006 |
ES |
PCT/ES06/70142 |
Claims
1. A computer-aided method for designing a smooth surface (13) for
a vehicle part covering an area of the surface of its body (11)
organized around an axis X, comprising the following steps: a)
Providing data indicating the profile, area and the position of a
plurality of sectors (15) delimited between said smooth surface
(13) and said body (11) by hypothetical planes perpendicular to
axis X; b) Generating a surface from the data provided in step a)
by homogenizing the order and the nodal vector of each of the
profiles (Pi) of said sectors (15) and applying homotheties to them
with origin in their lower point (21) so that the chords are equal;
c) Modifying N1 equidistant profiles (Py) of the surface generated
in the previous step by applying homotheties to them with origin in
a point (23) defining their position with respect to the body (11)
until their area (APy) corresponds to that of the profile located
in the same position of axis X in a reference area curve (19) made
from the data provided in step a) such that it defines a smooth
distribution of areas along axis X; d) Generating a surface from
the profiles (Py) resulting from the previous step and validating
that it adjusts to the reference area curve (19) by using N2
equidistant profiles of said surface, where N2>N1. If this is
not the case, step c) is repeated increasing the value of N1 unless
the latter prevents obtaining a smooth surface (13) with the data
provided in step a).
2. A computer-aided method for designing a smooth surface (13) for
a vehicle part according to claim 1, characterized in that said
part is the hull of an aircraft.
3. A system for designing a smooth surface (13) for a vehicle part
covering an area of the surface of its body (11) organized around
an axis X, comprising a computer comprising at least one memory and
a processor and an executable software residing in the memory of
said computer which is able to carry out the following operations
together with the computer: a) Storing data indicating the profile,
the area and the position of a plurality of sectors (15) delimited
between said smooth surface (13) and said body (11) by hypothetical
planes perpendicular to axis X; b) Generating a surface from said
starting data by homogenizing the order and the nodal vector of
each of the profiles (Pi) of said sectors (15) and applying
homotheties to them with origin in their lower point (21) so that
their chords (25) are equal; c) Modifying N1 equidistant profiles
(Py) of the surface generated in the previous operation by applying
homotheties to them with origin in a point (23) defining their
position with respect to the body (11) until their area (APy)
corresponds to that of the profile located in the same position of
axis X in a reference area curve (19) made from the starting data
such that it defines a smooth distribution of areas along axis X;
d) Generating a surface from the profiles (Py) resulting from the
previous operation and validating that it adjusts to the reference
area curve (19) by using N2 equidistant profiles of said surface,
where N2>N1. If this is not the case, the previous operation is
performed again increasing the value of N1 unless the latter
prevents obtaining a smooth surface (13) with the starting
data.
4. A system for designing a smooth surface (13) for a vehicle part
according to claim 3, characterized in that said part is the hull
of an aircraft.
5. A data signal in the form of a digital data flow for designing a
smooth surface (13) for a vehicle part covering an area of the
surface of its body (11) organized around an axis X in the
following steps: a) Obtaining data indicating the profile, area and
the position of a plurality of sectors (15) delimited between said
smooth surface (13) and said body (11) by hypothetical planes
perpendicular to axis X; b) Generating a surface from the data
provided in step a) by homogenizing the order and the nodal vector
of each of the profiles (Pi) of said sectors (15) and applying
homotheties to them with origin in their lower point (21) so that
their chords (25) are equal; c) Modifying N1 equidistant profiles
(Py) of the surface generated in the previous step by applying
homotheties to them with origin in a point (23) defining their
position with respect to the body (11) until their area (APy)
corresponds to that of the profile located in the same position of
axis X in a reference area curve (19) made from the data provided
in step a) such that it defines a smooth distribution of areas
along axis X; d) Generating a surface from the profiles (Py)
resulting from the previous step and validating that it adjusts to
the reference area curve (19) by using N2 equidistant profiles of
said surface, where N2>N1. If this is not the case, step c) is
repeated increasing the value of N1 unless the latter prevents
obtaining a smooth surface (13) with the data provided step a).
6. A data signal in the form of a digital data flow for designing a
smooth surface (13) for a vehicle part according to claim 5,
characterized in that said part is the hull of an aircraft.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to method and system for
designing smooth surfaces for certain parts of aircrafts, ships,
automobiles or other types of vehicles and specifically for
surfaces of parts located on the main body of the vehicle.
BACKGROUND OF THE INVENTION
[0002] The use of parts located on the main body either in the
fuselage in the case of aircrafts or in the body in the case of
automotive vehicles is frequent in the design of aircrafts, ships,
automobiles or other types of vehicles.
[0003] These parts, including most of the hulls used in the
different types of vehicles mentioned are intended for purposes
such as the following:
[0004] Covering objects located in the outer part of the larger
surface, minimizing the aerodynamic drag.
[0005] Changing the aerodynamic features in certain areas.
[0006] Improving the appearance of the product.
[0007] In the known art, the design of the surface of these parts
is a very complex and expensive process entailing a significant
part of the total manufacturing cost, especially if it must respond
to aerodynamic conditionings.
[0008] The present invention is aimed at solving this drawback.
SUMMARY OF THE INVENTION
[0009] In a first aspect, this invention provides a computer-aided
method for designing a smooth surface for a vehicle part covering
an area of the surface of its body organized around an axis X,
comprising the following steps:
[0010] Providing data indicating the profile, area and the position
of a plurality of sectors delimited between said smooth surface and
said body by hypothetical planes perpendicular to axis X.
[0011] Generating a surface from the data provided in the previous
step by homogenizing the order and the nodal vector of each of the
profiles of said sectors and applying homotheties to them with
origin in their lower point so that their chords are equal.
[0012] Modifying N1 equidistant profiles of the surface generated
in the previous step by applying homotheties to them with origin in
a point defining their position with respect to said body until
their area corresponds to that of the profile located in the same
position of axis X in a reference area curve made from the data
provided in the first step such that it defines a smooth
distribution of areas along axis X.
[0013] Generating a surface from the resulting profiles of the
previous step and validating that it adjusts to the reference area
curve by using N2 equidistant profiles of said surface, where
N2>N1. If this is not the case, the previous step is repeated
increasing the value of N1 unless the latter prevents obtaining a
smooth surface with the data provided in step a).
[0014] In a second step, the present invention provides a system
for designing a smooth surface for a vehicle part covering an area
of the surface of its body organized around an axis X, comprising a
computer comprising at least one memory and a processor and an
executable software residing in the memory of said computer which
is able to carry out the following operations together with the
computer:
[0015] Storing data indicating the profile, the area and the
position of a plurality of sectors delimited between said smooth
surface and said body by hypothetical planes perpendicular to axis
X in the memory of the computer.
[0016] Generating a surface from said starting data by homogenizing
the order and the nodal vector of each of the profiles of said
sectors and applying homotheties to them with origin in their lower
point so that the chords are equal.
[0017] Modifying N1 equidistant profiles of the surface generated
in the previous operation by applying homotheties to them with
origin in a point defining their position with respect to said body
until their area corresponds to that of the profile located in the
same position of axis X in a reference area curve made from the
starting data such that it defines a smooth distribution of areas
along axis X.
[0018] Generating a surface from the resulting profiles of the
previous operation and validating that it adjusts to the reference
area curve by using N2 equidistant profiles of said surface, where
N2>N1. If this is not the case, the previous operation is
performed again increasing the value of N1 unless the latter
prevents obtaining a smooth surface with the starting data.
[0019] In a third aspect, the present invention provides a data
signal in the form of a digital data flow for designing a smooth
surface for a vehicle part covering an area of the surface of its
body organized around an axis X in the following steps:
[0020] Obtaining data indicating the profile, area and the position
of a plurality of sectors delimited between said smooth surface and
said body by hypothetical planes perpendicular to axis X.
[0021] Generating a surface from said data by homogenizing the
order and the nodal vector of each of the profiles of said sectors
and applying homotheties to them with origin in their lower point
so that their chords are equal.
[0022] Modifying N1 equidistant profiles of the surface generated
in the previous step by applying homotheties to them with origin in
a point defining their position with respect to said body until
their area corresponds to that of the profile located in the same
position of axis X in a reference area curve made from the data
provided in the first step such that it defines a smooth
distribution of areas along axis X.
[0023] Generating a surface from the resulting profiles of the
previous step and validating that it adjusts to the reference area
curve by using N2 equidistant profiles of said surface, where
N2>N1. If this is not the case, the previous operation is
performed again increasing the value of N1 unless the latter
prevents obtaining a smooth surface with the data provided in the
first step.
[0024] The present invention is considered to be particularly
advantageous for designing the surfaces of aircraft hulls, without
affecting its applicability to the design of the surface of other
vehicle parts.
[0025] Other features and advantages of the present invention will
be evident from the following detailed description of the
illustrative embodiments of the object thereof together with the
attached figures.
DESCRIPTION OF THE FIGURES
[0026] FIGS. 1, 2 and 3 show schematic perspective views of the
smooth surface designed according to the present invention and of
the body on which it is located in different orientations.
[0027] FIG. 4 shows a plurality of sectors delimited between the
smooth surface designed according to the present invention and of
the body on which it is located by planes perpendicular to axis
X.
[0028] FIG. 5 shows several reference profiles of the smooth
surface designed according to the present invention and FIG. 6
shows those same profiles with their respective chords.
[0029] FIG. 7 shows the reference area curve of the smooth surface
designed according to the present invention.
[0030] FIGS. 8 and 10 show the area curves of the surface generated
during the design of the smooth surface according to the present
invention obtained from a different number of sectors.
[0031] FIG. 9 shows the reference area curve of the smooth surface
designed according to the present invention superimposed with an
area curve of a surface generated during said design.
DETAILED DESCRIPTION OF THE INVENTION
[0032] FIGS. 1, 2 and 3 show a vehicle part with a smooth surface
13 covering an area of its body 11 organized in relation to an axis
X designed according to the method object of the present invention
from the following starting data: a series of reference profiles
along axis X, a guide curve and a distribution of areas, which are
provided in a first step of the method.
[0033] The reference profiles Pi provided as starting data are a
set of flat curves defining the desired shape of a plurality of
sectors 15 (see FIG. 4) delimited between said smooth surface 13
and the body 11 by hypothetical planes perpendicular to axis X.
[0034] By way of example, FIG. 5 shows four reference profiles Pi
indicating the desired shape of four sectors 15 of the smooth
surface 13 located in the position i in axis X.
[0035] In a preferred embodiment, those reference profiles Pi are
provided in an IGES (Initial Graphics Exchange Specification) file.
Their design can be done by means of any graphic design program
which allows creating shapes with curvature continuity and the
result of which can be saved in files with IGES format.
[0036] As will be seen below, in each of those reference profiles
Pi it is possible to identify a lower point 21 of intersection with
the body 11 and a central point 23 representing its position in
relation to the body 11.
[0037] A guide curve 17 (see FIG. 3), which is the curve in which
the central points 23 of the reference profiles Pi will be located,
is also provided as starting data.
[0038] In a preferred embodiment, the guide curve 17 is provided as
an IGES file.
[0039] The distribution of areas is a set of values of the areas of
a plurality of sectors 15 (see FIG. 4) delimited between said
smooth surface 13 and the body 11 by hypothetical planes
perpendicular to axis X.
[0040] This distribution is an important factor to achieve the
smooth surface 13 with good aerodynamic features. In this sense,
the axis X around which the body 11 is organized coincides with the
direction of the hypothetical flow of current falling therein.
[0041] In a preferred embodiment of the present invention, this
distribution of areas is provided in the form of an ASCII file
containing the value Aj of the area of the corresponding sector 15
for a set of coordinates j in axis X.
[0042] A reference area curve 19 (see FIG. 7) is obtained from this
distribution of areas approximating the set of values Aj by means
of a curve of order 3 generating a smooth distribution of areas,
although it does not exactly represent the set of values Aj (8 in
FIG. 7).
[0043] Together with the smoothness requirement, the distribution
of areas is a fundamental factor in a surface intended to be used
with aerodynamic purposes.
[0044] From the reference profiles Pi and the guide curve 17 and in
a second step the design of the smooth surface 13, a surface is
generated by modifying the order and nodal vector of each of the
reference profiles Pi until reaching the values suitable for the
order desired for the smooth surface 13, which is achieved by
increasing the order and adding or eliminating nodes from each of
the reference profiles Pi. Once the homogeneity in the order and
nodal vector of all the profiles Pi has been achieved, a homothety
with origin in the lower point 21 is applied to them so that the
chords 25 (see FIG. 6) of all the profiles Pi are equal.
[0045] For the purposes of the invention, it must be understood
that the generation of the mentioned surface is a process that is
conceptually similar to classic process, known as skinning or
lofting, for the creation of a surface from a series of flat curves
using a mathematical methodology based on the so-called NURBS (Non
Uniform Rational B-splines).
[0046] As it is an undetermined problem, because there are infinite
surfaces which are supported on a series of flat curves, in the
period of manual craftsmanship the problem was solved thanks to a
master, a person with a lot of experience who adjusted a good
surface by means of mechanical devices (French curves, etc).
[0047] Since the 80s, this problem could be solved using a
mathematical methodology based on NURBS providing a unified
formulation for any type of surface, including conical surfaces,
the algorithms further being quick and stable from the computer
point of view. The task of the old lofting expert is now translated
into choosing the orders U and V of the surface and the so-called
nodal vectors in a suitable manner. The orders are usually not
greater than 5, but the possible nodal vectors are infinite, and it
also very difficult to guess their influence on the result,
therefore CAD systems are provided with help tool for that purpose.
In any case the precise choice of relevant parameters optimizes the
process as occurs in the method according to the present
invention.
[0048] The surface obtained in this second step is a sort of
"deformed cylinder" with the same diameter in all its sections.
[0049] In the third step of the design of the smooth surface 13,
the surface obtained in the second step is modified so that it
complies with the distribution of areas reflected in the reference
area curve 19. This is carried out as follows.
[0050] N1 equidistant sectors 15 of the surface resulting from the
previous step are obtained, the profiles Py of which are modified
by means of homotheties with origin in the central point of each
profile Py (the one located in the guide curve 17) in an iterative
process until achieving that their area APy (see FIG. 8) coincides
with the corresponding area in the reference area curve 19 for the
coordinate y. The number N1 of profiles Py (8 in FIG. 8) is
determined by the desired order for the smooth surface 13 in
direction X.
[0051] A new surface is generated from the profiles Py in a manner
similar to the one mentioned previously.
[0052] In the fourth step of the design of the smooth surface 13,
it is verified in detail whether the surface resulting from the
previous step complies with the distribution of areas reflected in
the reference area curve (19). This is carried out as follows.
[0053] N2 equidistant vectors of the surface resulting from the
previous step are obtained, where N2 is greater than N1. The value
of N2 is preset in advance and in a preferred embodiment is of the
order of 50.
[0054] As shown in FIG. 9 in which the area curve 29 corresponding
to said N2 vectors is superimposed with the reference area curve
19, the difference 31 between the sum of the areas of both curves
is obtained.
[0055] If this difference 31 exceeds a preset value, the third step
is repeated increasing the value of N1 unless its exceeds a preset
value for obtaining a smooth surface, in which case the process is
aborted because it is not possible to obtain a surface complying
with the required conditions.
[0056] In the event of repeating the third step and as shown in
FIG. 10, a new number N1 of equidistant sectors 15 of the surface
resulting from the previous step is obtained, the profiles P'y of
which (10 in FIG. 10) would be modified until achieving that their
area AP'y coincides with the corresponding area in the reference
area curve 19 for the coordinate y.
[0057] As the person skilled in the art will understand, the
implementation of the embodiment of the present invention that has
just been described and of other embodiments thereof can be carried
out in an individual computer, in a computer network or in any
computing device that can work with a CAD type program.
[0058] Any modifications comprised within the scope of the
following claims can be introduced in the preferred embodiment
which has been described.
* * * * *